The effect of modified polymer on the change rule of physical properties of different gradation coal gangue

In this study, in order to improve the water retention of coal gangue matrix and accelerate the recovery of frozen soil layer in mining area, three different particle size gradations of coal gangue and modified polymer SAP (0.0, 0.1, 0.2, 0.3, 0.4%) were compounded and reconstructed. Based on the indoor soil column model, the change rule of SAP on the physical properties of coal gangue with different gradations is clarified. The results show that SAP can promote the reconstruction of coal gangue matrix. When the mass fraction of SAP is constant, the partial soil gradation reduces the bulk density, and improves the total porosity, capillary porosity and capillary water holding capacity. The inhibition degree of SAP on capillary water migration was different. The sand, soil and viscosity gradations without SAP reached the design height at 1340, 1380 and 1470 min, respectively. When SAP was 0.0% ~ 0.4%, the higher the dosage, the longer the action time. After continuous measurement for 6 days under natural ventilation, SAP was 0.3%. The partial soil gradation had strong water retention performance and could effectively inhibit water loss. With the increase of time, the water loss was the slowest. It is recommended that the preferred SAP mass fraction is 0.3%, the gradation is partial soil, and the bulk density is 1.30 g/cm³, which can provide suitable water and gas conditions for vegetation growth.